1. Field of the Invention
The present invention relates to a multilayered printed wiring board, e.g., which is employed as a module board in a portable device and a method for manufacturing the multilayered printed wiring board.
2. Description of the Related Art
Recently, the downsizing and the weight saving for a portable device such as a cellular phone are developed and moreover, the performance of the portable device is developed. In addition, some instruments are combined with one another in the portable device. In this case, a multilayered printed wiring board is employed as the module board in the portable device. In view of the above-described requirements for portable device, it is desired to downsize, thin and grow in density the multilayered printed wiring board. In addition, some hardness and flexibility are required for the multilayered printed wiring board. For example, the hardness is required to realize the mechanical strength of the multilayered printed wiring board. The flexibility is required to house the multilayered printed wiring board in a narrow case under the bending condition.
Conventionally, a rigid-flexible wiring board is employed so as to satisfy the hardness and the flexibility. The applicant proposed a new type rigid-flexible wiring board in Reference 1 so as to develop the material yield. In Reference 1, the rigid wiring board and the flexible wiring board are laminated via a semi-hardened prepreg and pressed under the heating condition. In this case, the wiring pattern of the rigid wiring board is electrically connected with the wiring pattern of the flexible wiring board via interlayer connection conductors such as conductive bumps through the prepreg. In Patent Reference 1, the intended rigid-flexible wiring board is fabricated through the above-described manufacturing process.
[Reference 1] JP-A No. 2005-322878 (KOKAI)
In Reference 1, the intended rigid-flexible wiring board can be easily fabricated from the rigid wiring board and the flexible wiring board at higher material yield, but can not satisfy the downsizing of the board because the number of electric/electronic component can not be reduced.